Collector for electron tubes

ABSTRACT

In order to improve the cooling of the collector of a travelingwave tube, the latter is surrounded by an outer sleeve and insulating rods are inserted between the collector 30, and the sleeve. The sleeve is fixed on one side of an intermediate insulating member, on the opposite side of which the remainder of the tube is mounted.

United States Patent [72] Inventor Dominique Henry Paris, France [21] Appl. No. 20,208

[22] Filed Mar. 17, 1970 45 Patented Oct. 12, 1971 [73] Assignee Thomson-CSF [32] Priority Mar. 28, 1969 [33] France [54] COLLECTOR FOR ELECTRON TUBES 4 Claims, 4 Drawing Figs.

[52] US. Cl 313/39,

313/292, 313/288, 315/35, 315/393 [51] Int. Cl .4 H01j 25/34 [50] Field of Search 313/39, 292, 288; 331/182; 315/35, 39.3

[5 6] References Cited UNITED STATES PATENTS 2,827,589 3/1958 Hines 315/393 3,453,473 7/1969 Oess 313/292 Primary Examiner-John Kominski Attorney-Kurt Kelman ABSTRACT: in order to improve the cooling of the collector of a traveling-wave tube, the latter is surrounded by an outer sleeve and insulating rods are inserted between the collector 30, and the sleeve. The sleeve is fixed on one side of an intermediate insulating member, on the opposite side of which the remainder of the tube is mounted.

COLLECTOR FOR ELECTRON TUBES The present invention relates to electron tubes and more particularly to travelling-wave tubes.

Such tubes generally comprise a cylindrical evacuated envelope inside which the various components of the tube are mounted, while means are provided for coupling the tube to the input and output circuits.

One of these components is the collector which collects the electron beam once it has propagated through the tube. Except for the losses and for the energy fraction which is converted into the high-frequency energy, the whole of the energy of the beam is collected by the collector. This energy is currently in the order of several watts, even in the smallest models.

The dissipation of this power through the evacuated space which, in accordance with this technology, separates the collector from the envelope, is not an easy matter.

It is also known to make the collector a part of the envelope, the latter in this case being made up of two metal parts insulated from one another. This arrangement facilitates the dissipation of the power received by the collector, but complicates the manufacture of the tube: as a matter of fact, the forward part of the envelope, that is to say that containing the electron gun and the delay line, is usually at the potential of the delay line itself, that is to say the highest potential in the tube, while the collector part is at a lower potential in order to decelerate the electrons prior to their impact on the collector. The potentials concerned are for example 3,000 v., and 1,500 v., respectively. On the other hand, in operation, for safety reasons, the forward part of the envelope is earthed. For the same reasons, the collector is surrounded by a sleeve or jacket, which is also earthed.

Thus, in conventional travelling-wave tubes, the collector is always located inside either the envelope proper or a jacket or sleeve surrounding the envelope.

It is an object of the present invention to provide an arrangement which is both simpler'and more efficient, as far as dissipation of heat from the collector is concerned, than the prior art arrangements.

According to the invention there is provided an electron tube portion comprising an elongated collector for collecting electrons at the end of their trajectory, a sleeve surrounding said collector and spaced apart therefrom, bars of insulating material interposed between said collector and said sleeve, and an intermediate member having two ends, to one end of which said sleeve is fixed and the other end of which is arranged for connection to another portion of said tube.

For a better understanding of the invention and to show how the same may be carried into effect, reference will be made to the drawing accompanying the ensuing description and in which:

FIGS. 1 and 2 show schematically in axial section that part of the travelling-wave tube to which the invention relates, as it appears in known tubes.

FIGS. 3 and 3a show enlarged sectional views of the same part of a travelling-wave tube, modified in accordance with the invention.

In FIG. 1, the collector 12 is located inside the envelope 13 of a travelling-wave tube, opposite the end of a helical delay line through which the electron beam propagates in the direction of the arrow 11. In FIG. 1, the envelope 13 is made of metal in the zone illustrated. The collector forms a part of the envelope in the arrangement of FIG. 2.

In both cases, the collector 12 is brought through lead 12 to a negative potential in relation to the envelope 13 and to the helical delay line 10. The latter is at a high potential and the envelope is grounded, as the FIGS. show. The collector 12 is insulated from the envelope 13 by the insulating body 12" (FIG. 1) or by the insulating ring 14 (FIG. 2). In the device of FIG. 2, for reasons of safety, the collector 12 is surrounded by a metal sleeve 15 which is also earthed; an insulating body, for example a ceramic ring 16, is placed between the collector 12 and the sleeve l5.

FIGS. 3 and 3a illustrate an embodiment of the invention; these FIGS. are limited to that portion of the tube to which the invention applies, that is to say the portion comprising the collector 12 and the neighboring part of the envelope.

These FIGS. show the collector 30 and a sleeve 31 forming part of the tube envelope and made of a material exhibiting good thermal conductivity, both parts being cylindrical and being disposed concentrically around the tube axis XX The sleeve 31 is attached in vacuumtight fashion, for example by welding or brazing, to a component 32 to which there is also attached in vacuumtight fashion the remainder of the tube (the latter not having been shown since it forms no part of the present invention).

In accordance with the invention, there are arranged around the collector 30, in the annular space defined between it and the sleeve 31, rods or bars of insulating material as the cross section AA of FIG. 3a shows.

The assembling takes place in the following manner:

The hollow cylinder 30, for example of copper, terminates at its rear end in a lead-in connection 33'. Contiguous rods 34, for example of alumina, are deposited around the collector 30 as shown in FIG. 3a, these rods 34 rest within a shoulder 30' formed in the collector 30.

At this stage of assembly, the rods 34 are held in position by temporary fixings, for example collars, at two or three points.

The dimensions of the subassembly thus formed are such that it can be only force-fitted into the sleeve 31. The latter is, for example, of stainless steel and the subassembly is inserted therein coaxially therewith, for example by means of an appropriate press, the temporary fixings referred to earlier being removed progressively. When the subassembly is completely assembled in the sleeve 31, the intermediate member 32 is also force-fitting into the sleeve until its end rests on the shoulder 32. In the final position, the space 35 between the collector 30 and the intermediate member 32 is reduced to the minimum necessary for avoiding any risk of flash, in order to reduce to a minimum the electronic lens effect between these two components. Subsequently, the member 32 is welded to the sleeve 31, for example by electron bombardment.

During this force-fitting operation, the rods 34 are trapped between the sleeve 31, with which they are in contact along their generatrices, and the collector 30 into which they penetrate to a certain extent, the collector 30 being of softer metal than the sleeve 31.

The metals of which the collector 30 and the sleeve 31 are made are furthermore chosen to have such respective coefficients of thermal expansion that this cold weld effect is not modified by the heat treatments to which the tube is subjected during its manufacture, for example the baking operations at 400 to 450 C, which are the maximum temperatures reached during manufacture. These coefficients of thermal expansion should be such that the annular space between the collector 30 and the sleeve 31, should at any time during the phases of increasing temperature, taking into account the thermal expansion of the bars 34, be sufficient for accommodating the latter, so that at any instant the depth to which the bars 34 penetrate into the collector 30 does not increase, thus avoiding that on cooling, the contact between the bars 34 and the sleeve 31 may be lost, which might severely impair the necessary heat transfer between the collector 30 and the sleeve 31. This does not mean that for the sleeve 31 a metal should be chosen which has a coefficient of thermal expansion which is higher than that of the collector 30, because, even if the contrary were the case, the desired condition could be achieved, given the low value of the coefiicients of thermal expansion of the insulating materials of the bars 34 in relation to those of the metals of the collector 30 and the sleeve 31. On cooling, the bars revert to their initial position in relation to the collector 30 and the sleeve 31.

It should be noted that in operation, because of the temperature gradient perpendicularly to the axis X'X of the tube the collector being hotter than the sleeve, the contact between the rods 34 on the one hand and the collector 30 and sleeve a hollow cylinder of copper with an external radius l.5 mm. and a coefficient of thermal expansion of l70.l"/A&L C.

: a stainless steel tube with an internal radius of 2.5 mm. and a coefficient of thermal expansion of I60. C.

: Aluminum rods ol'diarneter of l mm.

with a coefficient of thermal expansion of 50.l0"/ Cv Baking temperature Collector 30 Sleeve 3| Rods 34 It will be noted from this example, that the distance between the collector 30 and the sleeve 31 is greater and greater with respect to the diameter of the rods 34 as the temperature increases.

Of course the invention is not limited to the embodiment described and shown which was given solely by way of examle. p What is claimed is:

1. An electron tube portion comprising an elongated collector for collecting electrons at the end of their trajectory, a sleeve surrounding said collector and spaced apart therefrom, bars of insulating material interposed between said collector and said sleeve and an intermediate member having two ends to one end of which said sleeve is fixed and the other end of which is arranged for connection to the portion of said tube wherein said electrons propagate.

2. A tube as claimed in claim 1, wherein said bars are force fitted between said collector and said sleeve.

3. A tube as claimed in claims 1 or 2, wherein said bars are cylindrical rods, contacting each other along generatrices thereof.

4. A tube as claimed in one of the preceding claims in which said bars are of alumina and said collector of copper. 

1. An electron tube portion comprising an elongated collector for collecting electrons at the end of their trajectory, a sleeve surrounding said collector and spaced apart therefrom, bars of insulating material interposed between said collector and said sleeve and an intermediate member having two ends to one end of which said sleeve is fixed and the other end of which is arranged for connection to the portion of said tube wherein said electrons propagate.
 2. A tube as claimed in claim 1, wherein said bars are force fitted between said collector and said sleeve.
 3. A tube as claimed in claims 1 or 2, wherein said bars are cylindrical rods, contacting each other along generatrices thereof.
 4. A tube as claimed in one of the preceding claims in which said bars are of alumina and said collector of copper. 